Electric furnace.



N. TESTRUP & T. RIGBY. A

ELECTRIC FURNACE;

APPLICATION FILED no.6. 1911.

1,106,166, Patented Aug.4, 1914.

UNITED STATES PATENT OFFICE...

NILS TESTRUP, OF LONDON, ENGLAND, AND THOMAS RIGBY, OF DUMFRIES, SCOT- LAND, ASSIGNORS, BY MESNE ASSIGNMENTS, TO WETCARBONIZING LIMITED, OF

LONDON, ENGLAND.

ELECTRIC FURNACE.

Specification of Letters'latent.

Application filed December 6, 1911. Serial No. 66%,144.

Patented Aug. 4, 1914.

To all whom it may concern:

Be it known that we, NILs Tns'rRUr, a subject of the King of Great Britain and Ireland, and residing at 6 Broad Street Place, London, England, and THOMAS RIGBY, a subject of the King of Great Britain and Ireland, and residing at Station Hotel, Dumfries, Scotland, have invented certain new and useful Improvements in Electric Furnaces, of which the following is a specification.

This invention relates to improvements in connection with smelting operations and more particularly to such operations carried out in an electric smelting furnace and using peat as fuel. The processes hereinafter described are especially applicable to the smeltingof iron.

The electric furnace usually employed for iron smelting has certain disadvantages. The furnace consists of a shaft at the bottom of which is a crucible in which the electrodes are inserted. The charge which is fed into the top of the shaft becomes dried and reheated and partially reduced in the s aft before it enters the reduction zone proper in the crucible and the gases issuing from the shaft are returned by a fan or the like to the crucible to increase the circulation of heated gases up the shaft and to cool the roof of the crucible an amount'of surplus gas equal to that produced by the reactions in the furnace being continuously taken away. Now when working on this system the moisture present in the materials fed into the furnace is evaporated and accompanies the gases which are circulated back again to the crucible of the furnace with the consequence that the water vapor is decomposed in the crucible at the expense of the heat generated in the same as the amount of the same varies in practice during the operation, it also causes a variation of temperature in the crucible of the furnace.

The object of the present invention is to allow of carrying out smelting operations, more particularly those of the character above indicated more economically as regards the consumption of heat and the cost of apparatus and with greater regularity of working conditions than heretofore and to simplify such apparatus.

Further advantages which arise from employrnent of the methods and apparatus hereinafter referred to are a larger range 0 adjustability of working and very efficient heat transmission.

According to the present invention the gas which is to be returned to the crucible is taken off at such a point in the shaft that it is practically free from Water vapor or other substance having a cooling effect on the furnace, the remainder of the gas passing through the incoming charge in the usual way. A further feature of this invention consists in overcoming the necessity of separate coking or charring installations in smelting operations of this character by introducing the raw fuel e. g. wet carbonized peat 1n the form of press cakes or briquets or air dried peat, into the furnace and in effecting coking or charring in the upper portion thereof, the gases and products of distillation being preferably passed into the foul main of the ammonia recovery gas producer where, as is to be preferred, such an element is employed in the connection with the installation.

Another feature resides in admitting air when and as desired to the upper part of the shaft so that combustion to any desired degree can occur which not only allows of obtaining a high preheating under the most efficient conditions of heat transmissions but also by regulation of the amount of preheating obtained in this Way allows of relieving the electrical elements of some of their load. It is to be observed moreover that apart .from the good heat efliciency obtained by this method of preheating any heat supplied in this way is obtained without the conversion losses which are inevitable if the same heat is supplied in the crucible as electrical energy.

The accompanying dia ammatic draw-,

ings indicate in Figure 1 t e preferred form of the smelting process according to the present invention and in Fig. 2 a view by 4 way of explanation of the upper part of the shaft in the case where combustion is to be 7 allowed to occur therein.

. shaft are provided a series of passages, d,

connected to an annular duct, e, connected to a duct f, in which is a dust separator, f, and blower, g, which passes the gases drawn off from the points, 0!, through the duct it into the upper art of the crucible i in which the electrodes 7, are situated, the gas entering by twyers i branching from the annular duct 7'. As reducing agent, the charcoal obtained by charring of a further quantity of peat is employed and this charrin is effected in the furnace itself by intro ucing the pressed wet carbonized peat either partially or practically wholly water free directly into the hopper a in admixture with the other 1ngredients of the charge. The top of the shaft 5 is connected by a duct is to the stand pipe I of the producer 0 which is provided with valves m and n. The foul main 0 of the producer has a valve [2 and the scrubber of the plant is shown at g and the fan at r, the necessary air and steam being supplied to the grate of the producer by a blower or the like in the usual way.

In operation the mixed ingredients of the charge gradually descend the shaft 1) and are dried, the peat being at the same time charred or coked. The water vapor and the products of destructive distillation of the peat pass off by the pipe is and if the valves m, n and o are properly adjusted, pass with the producer gas into the scrubber. The charge continuing its descent comes into contact with hot reducing gases arising from the crucible and becomes preheated and partially reduced, the gases which are evolved from it passing partially out through the orifices d to be returned by the blower 9 into the crucible and partially ascending into the upper part of the shaft to assist in charring and drying and passing out also bythe duct is. .The charge eventually reaches the erucible wherein the principal reaction occurs. It will be seen that the charge when it reaches the level of the orifices d has been already dried and heated to a fairly elevated temperature and as the water vapor evolved therefrom has been swept out from the top of the shaft through the duct 7: the gases issuing from the orifices (I will be practically free fro-m water and the disadvantages above pointed out will be overcome, and therefore by the circulation of the same in the crucible and shaft, the efiiciency of the reduction is increased.

It will be understood that where wood charcoal is used as fuel, the wood may similarly be fed directly into the furnace with the other ingredients of the charge.

Provision is usually made for the recovery of both dust and tar as well as ammonia, in a producer plant of the nature indicated and consequently there is a great saving of apparatus by proceeding in the manner described as these materials can be recovered from the furnace gases with economy and ease in the producer plant itself. At the same time in passing through the various recovery apparatus together with the producer gas an intimate admixture of the gases is attained which is desirable as by this means a uniform quality of gas is obtained leaving the gas producer system. The surplus gas produced in the electric furnace may contain 50% more or less of CO when entering the upper portion of the shaft and this mixing with the products of distillation of the fuel gives a gas of high calorific value for adding to the comparatively low grade producer gas. It will thus be seen that by such an arrangement the producer gas is enriched while at the same time ammonia, tar, dust and moisture are recovered together with the same constituents in the producer gas in one and the same plant. The gases leaving the upper portion of the shaft may be passed through an exhauster or the like to raise the pressure sufiiciently to enter the foul gas main of the producer gas plant, or any desirable means may be adopted to prevent an excess of pressure in the electric crucible.

\Ve have found in practice that when making charcoal or coke from air dried peat or from cake or briquets of wet carbonized peat that the quality and hardness of the coke produced is mainly dependent on the pressure exerted during the briqueting or pressing of the fuel and that for most practical purposes it is independent of the temperature at which coking is carried on. This is different from ordinary coal coking practice, and this property of the material enables us to effect coking at comparatively low temperatures so that the surplus gases produced entering the upper portion of the furnace shaft for the purpose of distillation should be sufiicient to effect the necessary coking. It may however be desirable or necessary as above indicated to admit air,

have a higher temperature than that of the sensible heat of the gases entering the upper portion of the shaft to effect the burning of the limestone before entrance to the reduction zone or lower half of the shaft. This may be desirable so that the gases circulating continuously through the upper part of the crucible and upward through the lower portion of the shaft may consist mainly of CO undiluted by the CO given off by the burning of the limestone, as by this means a more efficient reduction of the ore -may be obtained in the shaft. Fig. 2 shows diagrammatically such an arran ement of the upper portion of the shaft 0 a furnace as shown in Fig. 1 like reference letters being here employed. The shaft above the outlets (Z is contracted as at u and 4 air is allowed to enter to any regulated extent by orifices t and burning in the gases at or near the contraction gives the desired preheating by virtue of the hot gases which are distributed intimately throughout the charge in the upper part of the shaft. A fan is provided at s which allows of varying the conditions in the shaft as previously indicated. It may be desirable to increase the length of the hot zone obtained in this way and as the temperature tends rapidly to fall as the distance from the point of combustion increases it may be desirable to effect the combustion in stages and for this purpose it may be desirable to provide a plurality of orifices at different heights in the shaft at each of which a part of the burning occurs. It is also to be noticed that the gases circulated through the crucible and upward through the shaft will contain CO owing to the reduction of the ore and this will probably be converted mainly to CO in passing through the electric furnace. Such conversion will be at the expense of the heat of the furnace and we prefer therefore to arrange for the CO from the limestone to be given off away from the lower portion of the shaft. In such a case it will be understood that the carbon dioxid from the limestone will be given off in the upper or distillation portion of the shaft and pass away into the foul main of the gas producer together with the other gases and vapors.

It may under certain circumstances be necessary to circulate a larger quantity of gases than usual for the purpose of cooling the roof of the crucible but this will in the present case be immaterial and to a certain extent beneficial because there will in such case be a more intimate and active contact of the heated gases in the shaft with the descending materials and consequently a more uniform and greater reduction of the ore is to be expected.

It is further to be noted that by treating the materials in this manner a coke oven which will otherwise be necessary is rendered unnecessary and a great heat economy is also obtained as well as simplicity in the arrangement of apparatus in connection with such installation. It is also to be observed that owing to the low temperature of distillation of the fuel while a good coke or charcoal will be obtained, yet a high yield of ammonia may be expected as there will be little disassociation of ammonia at the comparatively low temperature used.

It will be understood that the methods and apparatus above described in detail are referred to by way of example only and that the present invention may be aplied in many different ways and for diEerent purposes without departing from the spirit of the same.

Having now described our invention what we claim as new and desire to secure by Letters Patent is 1. An electric smeltin furnace comprising in combination a shaft having a gas outlet from the upper end thereof, a crucible at the lower end of the shaft, at least one electrode in said crucible and means placing the crucible in communication with the shaft at a point in the latter between the gas outlet and the crucible, as set forth.

2. An electric smelting furnace comprising in combination a shaft, charging means therefor and a gas outlet therefrom, said outlet being situated near the upper end of the shaft, a crucible at the lower end of the shaft, electrodes in said crucible and means conducting to the crucible gases withdrawn from the shaft at a point between the gas outlet therein and the crucible, as set forth.

3. An electric smelting furnace comprising in combination a shaft, charging means situated near the top thereof, a gas outlet from the shaft near the upper end thereof,

by-product recovery means receiving the gases which leave the shaft through said outlet therein, a crucible situated at the lower end of the shaft, electrodes in said crucible and a conduit to the crucible from said shaft, said conduit branching from the latter at a point between the crucible and the gas outlet in the shaft, as set forth.

4. An electric smelting furnace comprising in combination a shaft, charging means situated near the top thereof, a gas outlet from the shaft near the upper end thereof, ammonia recovery means receiving the gases which leave the shaft through said outlet therein, a crucible situated at the lower end of the shaft, electrodes in said crucible, a conduit to the crucible from said shaft, said conduit branching from the latter at a oint between the cruclbleand the gas out et in the shaft, and means admittin air to the shaft above said conduit in or er to effect preliminary coking of the material supplied to the furnace, as and for the purposes set forth.

In testimony whereof we have signed our 'names to this specification in the presence of two subscribing witnesses.

NILS TESTRUP. T. RIGBY. Witnesses to the signature of Nils Testru p Barman HARRY Ma'r'rnnws,

E. COURTNEY WALKER. Witnesses as to the signature of Thomas Rigby:

M. A'rxmsorr ADAM, Barman H. Marnmws. 

